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<head><meta charset="utf-8"><title>type tagged downcasting for executors and errors · wg-async-foundations · Zulip Chat Archive</title></head>
<h2>Stream: <a href="https://rust-lang.github.io/zulip_archive/stream/187312-wg-async-foundations/index.html">wg-async-foundations</a></h2>
<h3>Topic: <a href="https://rust-lang.github.io/zulip_archive/stream/187312-wg-async-foundations/topic/type.20tagged.20downcasting.20for.20executors.20and.20errors.html">type tagged downcasting for executors and errors</a></h3>

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<a name="234364172"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187312-wg-async-foundations/topic/type%20tagged%20downcasting%20for%20executors%20and%20errors/near/234364172" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jane Lusby <a href="https://rust-lang.github.io/zulip_archive/stream/187312-wg-async-foundations/topic/type.20tagged.20downcasting.20for.20executors.20and.20errors.html#234364172">(Apr 13 2021 at 17:03)</a>:</h4>
<p>following up on this thread: <a href="#narrow/stream/219381-t-libs/topic/split.20generic.20member.20access.20RFC.3F">https://rust-lang.zulipchat.com/#narrow/stream/219381-t-libs/topic/split.20generic.20member.20access.20RFC.3F</a></p>



<a name="234364334"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187312-wg-async-foundations/topic/type%20tagged%20downcasting%20for%20executors%20and%20errors/near/234364334" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jane Lusby <a href="https://rust-lang.github.io/zulip_archive/stream/187312-wg-async-foundations/topic/type.20tagged.20downcasting.20for.20executors.20and.20errors.html#234364334">(Apr 13 2021 at 17:04)</a>:</h4>
<p>I'm looking into splitting the downcasting implementation logic from the generic member access RFC into its own RFC because it was mentioned that it seemed similar to proposals related to executors</p>



<a name="234364362"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187312-wg-async-foundations/topic/type%20tagged%20downcasting%20for%20executors%20and%20errors/near/234364362" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jane Lusby <a href="https://rust-lang.github.io/zulip_archive/stream/187312-wg-async-foundations/topic/type.20tagged.20downcasting.20for.20executors.20and.20errors.html#234364362">(Apr 13 2021 at 17:04)</a>:</h4>
<p>this is the comment I'm referring to: <a href="https://github.com/rust-lang/rfcs/pull/2895#issuecomment-736683549">https://github.com/rust-lang/rfcs/pull/2895#issuecomment-736683549</a></p>



<a name="234364474"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187312-wg-async-foundations/topic/type%20tagged%20downcasting%20for%20executors%20and%20errors/near/234364474" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jane Lusby <a href="https://rust-lang.github.io/zulip_archive/stream/187312-wg-async-foundations/topic/type.20tagged.20downcasting.20for.20executors.20and.20errors.html#234364474">(Apr 13 2021 at 17:05)</a>:</h4>
<p>what I'm trying to figure out is what proposals was <span class="user-mention" data-user-id="263805">@Plecra</span> referring too?</p>



<a name="234364615"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187312-wg-async-foundations/topic/type%20tagged%20downcasting%20for%20executors%20and%20errors/near/234364615" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jane Lusby <a href="https://rust-lang.github.io/zulip_archive/stream/187312-wg-async-foundations/topic/type.20tagged.20downcasting.20for.20executors.20and.20errors.html#234364615">(Apr 13 2021 at 17:06)</a>:</h4>
<p>and once I know what proposals I'm hoping to collaborate to write an RFC for the logic that is shared between the executors and generic member access for errors proposals</p>



<a name="234365104"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187312-wg-async-foundations/topic/type%20tagged%20downcasting%20for%20executors%20and%20errors/near/234365104" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jane Lusby <a href="https://rust-lang.github.io/zulip_archive/stream/187312-wg-async-foundations/topic/type.20tagged.20downcasting.20for.20executors.20and.20errors.html#234365104">(Apr 13 2021 at 17:09)</a>:</h4>
<p>cc <span class="user-mention" data-user-id="116883">@tmandry</span> <span class="user-mention" data-user-id="119031">@Esteban Küber</span></p>



<a name="234366670"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187312-wg-async-foundations/topic/type%20tagged%20downcasting%20for%20executors%20and%20errors/near/234366670" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> tmandry <a href="https://rust-lang.github.io/zulip_archive/stream/187312-wg-async-foundations/topic/type.20tagged.20downcasting.20for.20executors.20and.20errors.html#234366670">(Apr 13 2021 at 17:18)</a>:</h4>
<p>so this could be one mechanism for interop across executors, as well as providing executor-specific extensions to Context</p>



<a name="234366777"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187312-wg-async-foundations/topic/type%20tagged%20downcasting%20for%20executors%20and%20errors/near/234366777" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> tmandry <a href="https://rust-lang.github.io/zulip_archive/stream/187312-wg-async-foundations/topic/type.20tagged.20downcasting.20for.20executors.20and.20errors.html#234366777">(Apr 13 2021 at 17:19)</a>:</h4>
<p>I’m not directly aware of the proposals that comment is referring to, I imagine there might be some on irlo</p>



<a name="234367964"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187312-wg-async-foundations/topic/type%20tagged%20downcasting%20for%20executors%20and%20errors/near/234367964" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jane Lusby <a href="https://rust-lang.github.io/zulip_archive/stream/187312-wg-async-foundations/topic/type.20tagged.20downcasting.20for.20executors.20and.20errors.html#234367964">(Apr 13 2021 at 17:27)</a>:</h4>
<p>ill do some digging</p>



<a name="234368664"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187312-wg-async-foundations/topic/type%20tagged%20downcasting%20for%20executors%20and%20errors/near/234368664" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jane Lusby <a href="https://rust-lang.github.io/zulip_archive/stream/187312-wg-async-foundations/topic/type.20tagged.20downcasting.20for.20executors.20and.20errors.html#234368664">(Apr 13 2021 at 17:31)</a>:</h4>
<p>not finding anything that looks related on irlo :/</p>



<a name="234368741"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187312-wg-async-foundations/topic/type%20tagged%20downcasting%20for%20executors%20and%20errors/near/234368741" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jane Lusby <a href="https://rust-lang.github.io/zulip_archive/stream/187312-wg-async-foundations/topic/type.20tagged.20downcasting.20for.20executors.20and.20errors.html#234368741">(Apr 13 2021 at 17:31)</a>:</h4>
<p>checking users now</p>



<a name="234385806"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187312-wg-async-foundations/topic/type%20tagged%20downcasting%20for%20executors%20and%20errors/near/234385806" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/187312-wg-async-foundations/topic/type.20tagged.20downcasting.20for.20executors.20and.20errors.html#234385806">(Apr 13 2021 at 19:24)</a>:</h4>
<p><span class="user-mention" data-user-id="220273">@Jane Lusby</span> I don't think there have been <em>specific</em> proposals, but we were definitely talking about possibly adding more fields to <code>Context</code></p>



<a name="234385847"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187312-wg-async-foundations/topic/type%20tagged%20downcasting%20for%20executors%20and%20errors/near/234385847" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/187312-wg-async-foundations/topic/type.20tagged.20downcasting.20for.20executors.20and.20errors.html#234385847">(Apr 13 2021 at 19:24)</a>:</h4>
<p>for example threading down a "task spawner" or other context like that</p>



<a name="234386784"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187312-wg-async-foundations/topic/type%20tagged%20downcasting%20for%20executors%20and%20errors/near/234386784" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jane Lusby <a href="https://rust-lang.github.io/zulip_archive/stream/187312-wg-async-foundations/topic/type.20tagged.20downcasting.20for.20executors.20and.20errors.html#234386784">(Apr 13 2021 at 19:31)</a>:</h4>
<p>I see</p>



<a name="234386822"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187312-wg-async-foundations/topic/type%20tagged%20downcasting%20for%20executors%20and%20errors/near/234386822" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jane Lusby <a href="https://rust-lang.github.io/zulip_archive/stream/187312-wg-async-foundations/topic/type.20tagged.20downcasting.20for.20executors.20and.20errors.html#234386822">(Apr 13 2021 at 19:31)</a>:</h4>
<p>so presumably the generic member access impl could be used to extract a closure that acts as said task spawner</p>



<a name="234386986"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187312-wg-async-foundations/topic/type%20tagged%20downcasting%20for%20executors%20and%20errors/near/234386986" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jane Lusby <a href="https://rust-lang.github.io/zulip_archive/stream/187312-wg-async-foundations/topic/type.20tagged.20downcasting.20for.20executors.20and.20errors.html#234386986">(Apr 13 2021 at 19:32)</a>:</h4>
<p>hmm</p>



<a name="234387268"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187312-wg-async-foundations/topic/type%20tagged%20downcasting%20for%20executors%20and%20errors/near/234387268" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jane Lusby <a href="https://rust-lang.github.io/zulip_archive/stream/187312-wg-async-foundations/topic/type.20tagged.20downcasting.20for.20executors.20and.20errors.html#234387268">(Apr 13 2021 at 19:34)</a>:</h4>
<p>not at all sure what that would look like</p>



<a name="234394437"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187312-wg-async-foundations/topic/type%20tagged%20downcasting%20for%20executors%20and%20errors/near/234394437" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/187312-wg-async-foundations/topic/type.20tagged.20downcasting.20for.20executors.20and.20errors.html#234394437">(Apr 13 2021 at 20:23)</a>:</h4>
<p><span class="user-mention silent" data-user-id="220273">Jane Lusby</span> <a href="#narrow/stream/187312-wg-async-foundations/topic/type.20tagged.20downcasting.20for.20executors.20and.20errors/near/234386822">said</a>:</p>
<blockquote>
<p>so presumably the generic member access impl could be used to extract a closure that acts as said task spawner</p>
</blockquote>
<p>I'm not sure what this "generic member access" refers to, tbqh :)</p>



<a name="234394499"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187312-wg-async-foundations/topic/type%20tagged%20downcasting%20for%20executors%20and%20errors/near/234394499" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/187312-wg-async-foundations/topic/type.20tagged.20downcasting.20for.20executors.20and.20errors.html#234394499">(Apr 13 2021 at 20:24)</a>:</h4>
<p>I was just imagining having a <code>dyn TaskSpawner</code> in the <code>Context</code> somehow</p>



<a name="234394602"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187312-wg-async-foundations/topic/type%20tagged%20downcasting%20for%20executors%20and%20errors/near/234394602" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/187312-wg-async-foundations/topic/type.20tagged.20downcasting.20for.20executors.20and.20errors.html#234394602">(Apr 13 2021 at 20:24)</a>:</h4>
<p>(there are some other challenges having to do with allocation)</p>



<a name="234569662"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187312-wg-async-foundations/topic/type%20tagged%20downcasting%20for%20executors%20and%20errors/near/234569662" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jane Lusby <a href="https://rust-lang.github.io/zulip_archive/stream/187312-wg-async-foundations/topic/type.20tagged.20downcasting.20for.20executors.20and.20errors.html#234569662">(Apr 14 2021 at 20:31)</a>:</h4>
<p>generic member access is just the random term I've come up with to refer with an object safe generic abstraction over the types of functions like <code>fn backtrace</code> / <code>fn source</code></p>



<a name="234569712"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187312-wg-async-foundations/topic/type%20tagged%20downcasting%20for%20executors%20and%20errors/near/234569712" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jane Lusby <a href="https://rust-lang.github.io/zulip_archive/stream/187312-wg-async-foundations/topic/type.20tagged.20downcasting.20for.20executors.20and.20errors.html#234569712">(Apr 14 2021 at 20:31)</a>:</h4>
<p>so its as if there was a <code>fn context&lt;T&gt;(&amp;self) -&gt; Option&lt;&amp;T&gt;</code> method on the error trait</p>



<a name="234569828"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187312-wg-async-foundations/topic/type%20tagged%20downcasting%20for%20executors%20and%20errors/near/234569828" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jane Lusby <a href="https://rust-lang.github.io/zulip_archive/stream/187312-wg-async-foundations/topic/type.20tagged.20downcasting.20for.20executors.20and.20errors.html#234569828">(Apr 14 2021 at 20:32)</a>:</h4>
<p>and we've set it up so you can work with trait objects, so it would be trivial to get a <code>&amp;dyn TaskSpawner</code> out for example</p>



<a name="234569943"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187312-wg-async-foundations/topic/type%20tagged%20downcasting%20for%20executors%20and%20errors/near/234569943" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jane Lusby <a href="https://rust-lang.github.io/zulip_archive/stream/187312-wg-async-foundations/topic/type.20tagged.20downcasting.20for.20executors.20and.20errors.html#234569943">(Apr 14 2021 at 20:33)</a>:</h4>
<p>the motivating use case was so I could get <code>SpanTrace</code> out of errors instead of <code>Backtrace</code>, but there was no way in hell it would ever become part of std so I had to make it generic</p>



<a name="234570215"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187312-wg-async-foundations/topic/type%20tagged%20downcasting%20for%20executors%20and%20errors/near/234570215" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jane Lusby <a href="https://rust-lang.github.io/zulip_archive/stream/187312-wg-async-foundations/topic/type.20tagged.20downcasting.20for.20executors.20and.20errors.html#234570215">(Apr 14 2021 at 20:34)</a>:</h4>
<p>my first pass implementation was basically <code>fn context(&amp;self, type: TypeId) -&gt; Option&lt;&amp;dyn Any&gt;</code>, with a helper method on <code>dyn Error</code> to allow monomorphization and to do the downcasting for you, then the implementor of an error type would need to switch on the <code>TypeId</code></p>



<a name="234570277"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187312-wg-async-foundations/topic/type%20tagged%20downcasting%20for%20executors%20and%20errors/near/234570277" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jane Lusby <a href="https://rust-lang.github.io/zulip_archive/stream/187312-wg-async-foundations/topic/type.20tagged.20downcasting.20for.20executors.20and.20errors.html#234570277">(Apr 14 2021 at 20:35)</a>:</h4>
<p><span class="user-mention" data-user-id="270901">@Nika Layzell</span> helped me make a nicer API for this via the <code>object-provider</code> and eventually <code>dyno</code> crates, and add support for DSTs and eventually non 'static types</p>



<a name="234583557"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187312-wg-async-foundations/topic/type%20tagged%20downcasting%20for%20executors%20and%20errors/near/234583557" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/187312-wg-async-foundations/topic/type.20tagged.20downcasting.20for.20executors.20and.20errors.html#234583557">(Apr 14 2021 at 22:00)</a>:</h4>
<p><span class="user-mention" data-user-id="220273">@Jane Lusby</span> interesting-- is there a write-up?</p>



<a name="234583736"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187312-wg-async-foundations/topic/type%20tagged%20downcasting%20for%20executors%20and%20errors/near/234583736" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jane Lusby <a href="https://rust-lang.github.io/zulip_archive/stream/187312-wg-async-foundations/topic/type.20tagged.20downcasting.20for.20executors.20and.20errors.html#234583736">(Apr 14 2021 at 22:02)</a>:</h4>
<p>not yet, that's what I was planning on making, was hoping to find other stakeholders working on executors that might be working on something similar before I started splitting it out in into it's own RFC</p>



<a name="234583806"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187312-wg-async-foundations/topic/type%20tagged%20downcasting%20for%20executors%20and%20errors/near/234583806" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jane Lusby <a href="https://rust-lang.github.io/zulip_archive/stream/187312-wg-async-foundations/topic/type.20tagged.20downcasting.20for.20executors.20and.20errors.html#234583806">(Apr 14 2021 at 22:02)</a>:</h4>
<p>sounds like there's nothing concrete yet so I will go ahead and start working on said RFC I think</p>



<a name="234587148"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187312-wg-async-foundations/topic/type%20tagged%20downcasting%20for%20executors%20and%20errors/near/234587148" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Ibraheem Ahmed <a href="https://rust-lang.github.io/zulip_archive/stream/187312-wg-async-foundations/topic/type.20tagged.20downcasting.20for.20executors.20and.20errors.html#234587148">(Apr 14 2021 at 22:33)</a>:</h4>
<p>I was looking into this a while back and dug up a couple relevant links:</p>
<ul>
<li><a href="https://github.com/rust-lang/rfcs/issues/2900">Custom Future Contexts</a></li>
<li><a href="https://github.com/rustasync/team/issues/7"> Add hooks sufficient to build task-local data</a></li>
<li><a href="https://github.com/rust-lang/futures-rs/issues/1196">Consider allowing futures to require specialized executors</a></li>
<li><a href="https://github.com/rust-lang/rfcs/pull/2592#issuecomment-462555711">Discussion in the stabilization PR</a></li>
<li><a href="https://github.com/rustasync/team/issues/56">Consider removing spawning from futures::task::Context </a></li>
</ul>



<a name="234589530"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187312-wg-async-foundations/topic/type%20tagged%20downcasting%20for%20executors%20and%20errors/near/234589530" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Ibraheem Ahmed <a href="https://rust-lang.github.io/zulip_archive/stream/187312-wg-async-foundations/topic/type.20tagged.20downcasting.20for.20executors.20and.20errors.html#234589530">(Apr 14 2021 at 22:58)</a>:</h4>
<p><span class="user-mention silent" data-user-id="220273">Jane Lusby</span> <a href="#narrow/stream/187312-wg-async-foundations/topic/type.20tagged.20downcasting.20for.20executors.20and.20errors/near/234583806">said</a>:</p>
<blockquote>
<p>sounds like there's nothing concrete yet so I will go ahead and start working on said RFC I think</p>
</blockquote>
<p><span class="user-mention" data-user-id="263805">@Plecra</span> mentioned writing  an RFC after <a href="https://github.com/rust-lang/rust/issues/2895">#2895</a> was merged. I know they are active on the rust-lang discord server, so you might want to reach out there.</p>



<a name="234601584"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187312-wg-async-foundations/topic/type%20tagged%20downcasting%20for%20executors%20and%20errors/near/234601584" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jane Lusby <a href="https://rust-lang.github.io/zulip_archive/stream/187312-wg-async-foundations/topic/type.20tagged.20downcasting.20for.20executors.20and.20errors.html#234601584">(Apr 15 2021 at 01:17)</a>:</h4>
<p>will do, thanks</p>



<a name="234763047"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187312-wg-async-foundations/topic/type%20tagged%20downcasting%20for%20executors%20and%20errors/near/234763047" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jane Lusby <a href="https://rust-lang.github.io/zulip_archive/stream/187312-wg-async-foundations/topic/type.20tagged.20downcasting.20for.20executors.20and.20errors.html#234763047">(Apr 15 2021 at 22:17)</a>:</h4>
<p>reached out to <span class="user-mention" data-user-id="263805">@Plecra</span> , they expressed interest in learning the RFC process so they're writing up the RFC for this now <span aria-label="blush" class="emoji emoji-1f60a" role="img" title="blush">:blush:</span></p>



<hr><p>Last updated: Aug 07 2021 at 22:04 UTC</p>
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